1. Technical Field
The present invention relates to a technique for detecting malicious calls, for example, spam and crank calls of IP phones.
Priority is claimed on Japanese Patent Application No. 2009-110816, filed Apr. 30, 2009, the content of which is incorporated herein by reference.
2. Background Art
Due to spread or generalization of the Internet, services using the Internet, for example, an e-mail service and a Web service are widely used in a general life. Further, in recent years, IP (Internet protocol) phones which can conduct voice communication via the Internet have been being generally used.
Today, the internet and various services using thereof are sufficiently provided, and on the other hand, in e-mail services, there is a social problem of e-mails which are called spam or junk mails and which are transmitted in a one-way manner while a person who receives such mails does not want. Further, such problematic actions are conducted in the IP phone as well. For example, by calling a phone number of an IP phone which is randomly selected or by successively calling a series of phone numbers, when a connection is successfully established, a voice messages is played back which is, for example, a recorded voice or a synthesized voice. Such a spam on the IP phone is called SPIT (Spam Over Internet Telephone) (for example, see Patent Document 1).
In conventional techniques, there is only one method for determining whether or not an incoming call of an IP phone is SPIT and that is by checking the user ID of the caller side IP phone. For example, user IDs of both dealers who transmit the SPIT and transmitters who are already known as specific persons (SPIT transmitters) are listed on a blacklist, user IDs of persons who are permitted communication are listed on a white list, and in accordance with such a method, incoming calls from SPIT transmitters who are already known are denied.    Patent Document 1: PCT Patent Application No. WO/2008/040539
However, the user IDs can be copied, and if the SPIT transmitter uses the user ID of a third person (a disguise) and makes a phone call (a disguised call), there is a possibility in which such a malicious call is accepted by evading the blacklist and passing through the white list. In such a case, the called person may respond to the call without detecting the disguised call.
The present invention is conceived to resolve the above-described problems and has an object to provide a malicious call detection apparatus, a malicious call detecting method and a computer program for detecting a malicious call that can improve detection accuracy.